A/D Development History

BitScope was originally designed to use the now discontinued Motorola MC10319 25MS/S ADC. The MC10319 is a bipolar chip design which combines wide bandwidth with completely static operation. It was a good choice for BitScope as it came in a 24 pin DIP package allowing future replacement by a PCB module. Its static bipolar design allowed simple software loops to control the timebase, and the direct conversion via a comparator tree meant no pipeline delay when sampling data.

Older ECL and bipolar chips like the MC10319 are no longer viable and most manufacturers have now discontinued them. They draw excessive power, and require old and expensive fabrication processes that are no longer used.

These days, most chips are CMOS which means they are cheap and fast. The most popular ADC after the Motorola device was the EXAR 8786 which is rated to 30MS/S. We offer this chip in a low cost replacement ADC module (pictured left) for use with BitScope. It is a good alternative to the MC10319 but while it can operate at a slightly higher sample rate it has a more limited input bandwidth.

More recently, a number of new technology ADC chips that promise much higher bandwidth and capture precision have been released by Texas Instruments, Analog Devices, National Semiconductor and others.

After extensive evaluation and testing, we have found the TI5540 ADC to be the best example of this new converter technology for use in BitScope, and our surface mount ADC module is based on this chip. It has excellent noise immunity and is fast enough to make full use of BitScope's 100 MHz analogue input bandwidth circuitry. Also, the TI5540's 2V input span matches the MC10319 maintaining exactly the same voltage ranges with both chips.